Recently I was advised that my Leningrad 4 light meter needed a battery to run. I was surprised, but as the person who mentioned this is well versed in Soviet photographics (and pointed out the small "hatch" on the back where he indicated the battery should go), I just assumed that as mine is working okay then the battery mustn't need replacing anyway...so why check the veracity of this statement?
On a whim, I was checking out the manual for this light meter on Butkus' website, and there we are: no batteries required. The selenium cell in the light meter basically receives a charge from any light, so it's quite self contained. Nifty.
I have no idea if selenium cells lose sensitivity over time. We'll see, I guess.
Just thought I'd share my discovery.